Many cutting tools have helical flutes through which chips are evacuated after being cut from a workpiece. The flutes tend to clog, and tool cutting efficiency is thereby reduced if the chips are not adequately removed; if this problem is not treated over time it can eventually lead to tool failure. To the extent that heat is also generated while a workpiece is being cut and the formed chips are being evacuated, care must also be taken for cooling liquid (or cooling air) to be properly introduced into the flutes.
The evacuation of chips is often complicated by even more significant heat generation. Particularly, when the flutes are partially or completely clogged, many chips often do not end up being exposed to the cooling liquid, thereby resulting in high friction and very high chip temperatures; as such, the extra heat generated thereby is transferred to the cutting surfaces. Accordingly, thermal cracking is liable to develop at the cutting edges, along with other types of wear deriving from excessive temperature variations caused by intermittent machining and an unreliable (e.g., fluctuating) supply of cooling liquid.
Based at least on the foregoing, it is recognized that it would be desirable to provide a structure within the flutes themselves that could help significantly reduce the thermal load to which cutting edges and flute surfaces are exposed.
U.S. Pat. No. 5,509,761 discloses a drill having a plurality of grooves that extend in the chip-discharging direction and are formed in an inner surface portion of each chip-discharging flute. This ensures a smoother discharge of chips by reducing the area of contact between the inner surface portion and the chips flowing therealong; consequently, this reduces the friction acting between such elements.
However, U.S. Pat. No. 5,509,761 is not instructive for treating problems encountered in end mills or other cutting tools that are involved in peripheral cutting operations; there, the peripheral cutting edge of the flutes is instrumental in chip formation as well as being involved in end face cutting operations, while a drill bit (e.g., as in U.S. Pat. No. 5,509,761) participates in an end cutting operation only at its point angle.
Thus, the flutes of U.S. Pat. No. 5,509,761 are used only for chip evacuation and are not exposed to cutting-derived friction.
In connection with the above, it can be noted that the grooves in U.S. Pat. No. 5,509,761 would be highly incapable of significantly dissipating any heat generated by a tool during a cutting operation or from chips being evacuated; this would hold true even if cooling liquid were present. Thus, while the noted grooves may be intended to reduce friction during the discharge of chips, they are not at all configured for promoting heat dissipation. Additional drawbacks that would be encountered in that regard include, but are not limited to: weakening of the flute, to the extent that the grooves are positioned throughout the flute inner surface; and a prospective negligible dwelling time of cooling liquid within a groove, wherein any potential cooling ability is significantly diminished based on a relatively rapid flow of cooling liquid through the continuous and elongated grooves.